An attorney for the US soldier on trial for giving classified information to WikiLeaks says his client was young and naive, but had good intentions.

Three years after his arrest in Iraq for allegedly causing America's largest intelligence leak, Private First Class Bradley Manning has finally gone on trial over his disclosures to the secrets sharing website.

In his opening statement, defence attorney David Coombs said Manning thought he could make the world a better place by releasing thousands of classified documents.

Mr Coombs said: "He believed this information showed how we value human life. He was troubled by that. He believed that if the American public saw it, they too would be troubled."

Image Caption:Protesters outside the military base in Fort Meade, Maryland

But prosecutors said the sensitive material fell into enemy hands, adding they will present evidence that Osama bin Laden asked for and received information given to WikiLeaks.

"This is a case about a soldier who systematically harvested hundreds of thousands of documents from classified databases and then dumped that information on to the Internet into the hands of the enemy," prosecutor, Captain Joe Morrow, said.

Mr Coombs did not address those accusations.

Manning - who faces a possible 154-year jail sentence - has admitted sending material to the website and offered to plead guilty to several offences but denies the most serious charge of knowingly aiding al Qaeda.

Supporters argue the 25-year-old former intelligence analyst's actions shone a light into the darkest corners of the US-led wars in Iraq and Afghanistan.

But opponents say he is a traitor whose actions endangered the lives of people around the world, including US citizens.

Image Caption:WikiLeaks founder Julian Assange is holed up at the Ecuadorian embassy

Manning was arrested in May 2010 while serving as a military intelligence analyst in Baghdad, but his case has been delayed due to the complexity of the charges he faces.

His lawyers successfully argued he had been subjected to unduly harsh detention methods and as a result he will receive a 112-day reduction of any eventual jail term.

He has offered to plead guilty to 10 offences, including breaches of military discipline, which could see him sentenced to 20 years under the court martial process.

But he could face a maximum 154 years in jail if found guilty of "aiding the enemy".

A Navy Seal who participated in the May 2011 raid that killed Osama bin Laden at his hideout in Pakistan is expected to testify in the trial among dozens of witnesses.

Part of the US government's case against Manning asserts that the former al Qaeda leader had asked an aide to retrieve documents from the internet that Manning had passed to WikiLeaks.

The trial is expected to last 12 weeks.

WikiLeaks founder Julian Assange has been living in the Ecuadorian embassy in London since last June after being granted political asylum.

He is wanted for questioning for sexual assaults in Sweden but fears he will be extradited to the US for questioning over the publication of the confidential documents.

Ricardo Patino, Ecuador's Foreign Minister, is due to travel to Britain later this month to visit Mr Assange and has offered to hold talks with the Foreign Secretary William Hague on the issue.